In such a known writing instrument of this type, the tubular element generally has a feeler having a first end serving to come into contact with the medium during writing, and a second end connected to a movement detector mechanism for detecting movement of the feeler in contact with the medium. That movement detector mechanism is connected to the processor unit to enable the liquid spray system to be activated. Thus, when the user holds the writing instrument in the hand and moves it towards the medium, the feeler comes into contact with the surface of the medium, thereby enabling the detector mechanism to send a signal to the processor unit to activate spraying of the liquid.
Therefore, although the writing head, namely the liquid spray head, does not need to be in contact with the medium, it is nevertheless essential for the feeler of the writing instrument to be in contact with the medium in order to be able to start spraying the liquid. It can be inconvenient for the user to put the feeler into contact with the medium, in particular when said medium is rough to some extent.
In addition, since the end of the feeler in contact with the medium is generally close to the point of impact of the spray of liquid on the medium, there are major risks that the end of the feeler might come into contact with the liquid before it dries, thereby smearing it over the medium while the writing instrument is in normal use.
Finally, the feeler, which necessarily extends beyond the liquid spray head, can also be subjected to a sudden impact, giving rise to irreparable damage to the detector mechanism, thereby causing the entire writing instrument to be put out of operation.